1. Technical Field of the Invention
The present invention relates to adjustment of reproduction signal quality of data which is recorded on write once optical disks and erasable optical disks.
2. Prior Art
Optical disks are used for recording, reproducing, and backing up audio or music data, computer data, image or still picture data, motion picture data, and the like. This is because optical disks can record a large amount of data in addition to the spread of low price optical disks and optical disk recording apparatuses capable of recording data as well as data recording software and computers. Optical disks capable of recording data include write once optical disks such as CD-R and DVD-R that can record data only once; and erasable optical disks such as CD-RW, DVD−RW, DVD+RW, and DVD-RAM that can rewrite data. An optical disk recording apparatus for recording dada on optical disks automatically provides optimal values of machine parameters such as Write Strategy associated with the reproduction signal quality of recorded data. Occasionally, the conventional optical recording apparatus may automatically set an improper machine parameter. When using such an optical disk recording apparatus, a user can determine whether or not to enable adjusting the function of automatically decreasing an improper recording speed to a possibly workable level.
It is known that the sound quality slightly changes when music data on a pressed CD (such as a CD-DA manufactured by a stamper) is copied to the above-mentioned recordable optical disk. Since the optical disk records digital music data, there seems no difference in the sound quality between the original music data and the copied data. Actually, however, the music data causes a different sound quality perceivable by specialists or experienced listeners due to change of reproduction signal qualities such as a β value and a jitter.
Presently, though it is not clearly known why this difference occurs, it is known that the sound quality changes with a machine parameter related to the reproduction signal quality.
The conventional optical disk recording apparatus automatically provides optimal parameter values as mentioned above. Accordingly, the same optimal parameter is used to record data irrespectively of whether an optical disk records, e.g., music data or computer data. Though the optimal parameter is defined for the best effort to prevent an error during data reproduction, the parameter does not always ensure the best sound quality for music data recording. In order to provide good sound quality for reproduction of music data recorded on the optical disk, it is necessary to define an optimal parameter for music data independently of that for computer data.
When the conventional optical disk recording apparatus records data on an optical disk, however, a user cannot set a parameter for representing the reproduction signal quality of recorded data. When music data is recorded on a CD-R disk, for example, there has not been available parameter settings such as customizing the β value in order to improve the sound quality of reproduced music data. Such a design allows beginners to easily record data on optical disks, but has been unsatisfactory for advanced users because there is no way of customizing a parameter representing the reproduction signal quality.
Since optical disk materials (particularly for the recording layer) vary with types, manufacturers, models, and the like, the Write Strategy and recording speed settings for the optical disk recording apparatus also vary accordingly. When music data on a pressed CD is copied to a CD-R, sounds reproduced from the pressed CD and the CD-R may cause different sound qualities.
Further, depending on manufacturing periods, models, and the like, recordable optical disks are designed for different maximum possible recording speeds and different recording speeds capable of recording with the best signal quality. For example, an earlier model optical disk provides a low maximum recordable speed and uses a relatively thick recording film, making it possible to record data at low-speed areas such as 1× speed (normal speed) and 2× speed (double speed). By contrast, a recent model optical disk provides a high maximum recordable speed and uses a relatively thin recording film, making it possible to record data at high-speed ranges such as 4× speed (four times speed) and 8× speed (eight times speed). When the optical disk is incompatible with a recording speed inadvertently set by a user, some optical disk recording apparatuses have a function of automatically adjust the current recording speed to the maximum recording speed congruent with the optical disk. However, the adjusted maximum recording speed is based on the signal quality limit, not on the criterion of selecting a recording speed for good sound quality with reduced jitter, for example. Accordingly, the recording speed automatically set by this function does not necessarily ensure good sound quality for recording music data. This function specification has been unsatisfactory for some users such as experienced listeners who wish good sound quality.
To cope with this problem, for example, an experienced listener purchases an optical disk recording apparatus suitable for music data recording. The listener also purchases an optical disk that is compatible with such an optical disk recording apparatus and that is capable of recording music data with good sound quality. Further, he or she needs to adjust an optimal write speed for each of the selected optical disks. These works impose users with many costs and labors.
When a CD-R disk is recorded on the optical disk recording apparatus, that CD-R disk is not always reproduced on the same optical disk recording apparatus, but may be reproduced on a different CD player. In such a case, good reproduction signal quality on the optical disk recording apparatus does not necessarily mean good reproduction sound quality on another CD player.